New twist on bird threat to orchards

On the perch . . . Artificial perches are used to attract birds to vineyards in northern Victoria.

Birds that hang around crops may be doing more good than harm, according to a Charles Sturt University Albury campus ecologist.

Rebecca Peisley’s research into the benefits and costs of bird activity in agroecosystems was conducted across three different farming systems between 2014 and 2016. Some of the study was done on apple orchards in Shepparton.

The research found that apple yields could be improved by an average of 11 per cent.

‘‘It was pretty simple. I went out with commercial bird netting on some trees and left some open,’’ Dr Peisley said.

‘‘Then I counted how many (of the fruit) had insect damage on what could be reached and what couldn’t.

‘‘Then I calculated the yield percentage difference. In some cases it was higher and some cases not so much, but yield percentage was 11 per cent on average.’’

Dr Peisley also looked at the benefits birds have at vineyards and cattle grazing paddocks.

‘‘In apple orchards, birds were overwhelmingly positive. Damage to apples was just two per cent and insect damage was reduced by up to 20 per cent,’’ she said.

‘‘In vineyards in northern Victoria, in Glenrowan and Rutherglen, I installed artificial perches.

‘‘(There were) not many birds of prey, but magpies loved them. Smaller birds thought the magpies were birds of prey.

‘‘It was like a negative reinforcement for the small purpose birds.’’

In vineyards, damage reduced from nine per cent down to four per cent, while in paddocks, Dr Peisley used rabbit carcases to see the benefits of birds.

‘‘In cattle grazing, I looked at birds removing rabbit carcases. Birds of prey and scavenging birds got to the carcases and removed them before foxes,’’ she said.

‘‘On average, 20 per cent were removed and on most occasions they would eat the whole rabbit.’’

Dr Peisley said on orchards, honey eaters, robins and kookaburras were most common and despite damage birds can cause to yields, feedback had been positive from farmers.

‘‘It’s been really positive from everyone so far,’’ she said.

‘‘As a scientist it is important to acknowledge, yes, birds are doing damage, but if you look over a whole season, you can see the difference.’’